use std::cmp::*; // https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 macro_rules! input { ($($r:tt)*) => { let stdin = std::io::stdin(); let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock())); let mut next = move || -> String{ bytes.by_ref().map(|r|r.unwrap() as char) .skip_while(|c|c.is_whitespace()) .take_while(|c|!c.is_whitespace()) .collect() }; input_inner!{next, $($r)*} }; } macro_rules! input_inner { ($next:expr) => {}; ($next:expr,) => {}; ($next:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($next, $t); input_inner!{$next $($r)*} }; } macro_rules! read_value { ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, usize1) => (read_value!($next, usize) - 1); ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error")); } /** * Union-Find tree. * Verified by https://atcoder.jp/contests/pakencamp-2019-day3/submissions/9253305 */ struct UnionFind { disj: Vec, rank: Vec } impl UnionFind { fn new(n: usize) -> Self { let disj = (0..n).collect(); UnionFind { disj: disj, rank: vec![1; n] } } fn root(&mut self, x: usize) -> usize { if x != self.disj[x] { let par = self.disj[x]; let r = self.root(par); self.disj[x] = r; } self.disj[x] } fn unite(&mut self, x: usize, y: usize) { let mut x = self.root(x); let mut y = self.root(y); if x == y { return } if self.rank[x] > self.rank[y] { std::mem::swap(&mut x, &mut y); } self.disj[x] = y; self.rank[y] += self.rank[x]; } #[allow(unused)] fn is_same_set(&mut self, x: usize, y: usize) -> bool { self.root(x) == self.root(y) } #[allow(unused)] fn size(&mut self, x: usize) -> usize { let x = self.root(x); self.rank[x] } } // https://yukicoder.me/problems/no/1668 (3) // (隣接しているとは限らない) 同じ値を UnionFind で繋げる。その後、隣接する連結成分について、小さい方から大きい方へ辺を張る。こうしてできたグラフは DAG なので、下から w[i] = max(w[i - 1], w[i に伸びている辺の始点] + 1) として更新すれば良い。 fn main() { input! { h: usize, w: usize, n: usize, c: [[usize1; w]; h], } let mut uf = UnionFind::new(h * w); let mut pl = vec![h * w; n]; for i in 0..h { for j in 0..w { let v = i * w + j; let c = c[i][j]; if pl[c] >= h * w { pl[c] = v; } else { uf.unite(v, pl[c]); } } } let mut g = vec![vec![]; n]; for i in 0..h - 1 { for j in 0..w { let h1 = c[i][j]; let h2 = c[i + 1][j]; if h1 < h2 { g[h2].push(h1); } else if h1 > h2 { g[h1].push(h2); } } } for i in 0..h { for j in 0..w - 1 { let h1 = c[i][j]; let h2 = c[i][j + 1]; if h1 < h2 { g[h2].push(h1); } else if h1 > h2 { g[h1].push(h2); } } } for i in 0..n { g[i].sort_unstable(); g[i].dedup(); } let mut dp = vec![0; n]; for i in 1..n { let mut ma = dp[i - 1]; for &w in &g[i] { ma = max(ma, dp[w] + 1); } dp[i] = ma; } println!("{}", dp[n - 1] + 1); }